The present invention relates to flexible cover or tarping systems for open-topped containers and particularly concerns a mechanism for locking the flexible cover or tarp extended over the container.
Many hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. In a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel and the like, as well as organic materials, such as grain or produce. Depending upon the nature of the materials stored in the open-topped container, it is often desirable to provide a cover for the container. A cover is particularly valuable when the containers are part of a vehicle, such as a dump truck. Rigid covers have given way to flexible cover systems that utilize a flexible tarpaulin (tarp) that can be drawn from a stowed position at one end of the container to a deployed position covering the open top of the vehicle container or bed. The flexible cover or tarpaulin is preferable in this arena because it can be easily stowed when the cover is not necessary, such as when a dump truck is being loaded or emptied. In addition, the flexible cover is generally easier to deploy than a rigid cover.
A variety of flexible cover or tarping systems have been developed that are geared toward particular hauling vehicle applications. One such tarping system is the Easy Cover® Tarping System manufactured and sold by Aero Industries, Inc. An example of one form of the Easy Cover® Tarping System is shown in FIG. 1. The vehicle 10 includes a dump body 11 with a flexible cover or tarp 13 sized to cover the entire open top of the dump body when in the deployed position shown in the figure. The vehicle is provided with a deployment and retraction mechanism that is operable to extend the tarp over the container and to retract the container to a stowed position. The tarp is stored within a storage assembly 14 that may be mounted toward the front of the vehicle 10, as reflected in FIG. 1 or that may be mounted on a movable bail arm assembly 16 used to extend the tarp to its deployed position. The storage assembly includes a roller assembly 15 that may rotatably mounted to the vehicle or to the movable bail arm, and is configured to roll up the tarp 13 to its stowed position and to unfurl the tarp as it is pulled away from the roller assembly. The bail arm assembly 16 is connected to a free end of the tarp 13 and is configured to draw the tarp out of the roller assembly 14 as the bail arm assembly sweeps over the dump body. In the illustrated embodiment, the storage assembly includes a housing 18 mounted to the front of the dump body 11. A drive assembly 12 may be mounted to the housing 18 that is operable to retract the tarp back into the housing. The drive assembly may be motorized or manual but is configured to rotate the roller assembly to continuously wind the tarp thereon.
One problem that is persistently faced with tarping systems of the type shown in FIG. 1 is the effect of air flow or wind as the vehicle is traveling. This problem becomes especially acute at high speeds. If the tarpaulin 13 is not properly restrained in its deployed position it can be damaged by flapping and whipping over the top of the dump body. Road vibration can have a similar effect on the tarp. This excess movement of the tarp can cause it to unroll from the roller assembly 15 even when the free end of the tarp is held at the rear end of the dump body. This unrolling leads to more flapping of the tarp, particularly when traveling at highway speeds, causing more damage to the tarp and even to the storage assembly 14 and dump body.
In order to address this problem, various systems have been devised to hold the tarp down against the container body. In one common system, a web of cords is laid over the tarp cover along the length of the container body and attached to mounts fixed to the side of the body. In other systems, the bail member includes a tie down that can be manually attached to mounts at the rear of the body. Still other systems rely upon a complicated array of mechanical, electrical or hydraulic structures to apply a constant tension along the length of the tarp. However, in most cases, the tension along the length of the tarp does not alleviate the problem of bellowing of the side edges of the tarp or bouncing of the bail member.
In other systems, a separate hold-down arm assembly is provided that bears against a forward portion of the tarp to hold it against the top rail of the dump body. This type of hold-down system is typically self-deployed and less complicated than the other approaches discussed above. However, even with this type of system tarp billowing or vibration can still cause the tarp to gradually unroll. Moreover, these types of hold-down systems have difficulty in generating enough force or torque to keep the cover pressed against the top rail of the dump body, especially at highway speeds. Consequently, there is a need for a system that can positively lock the tarp or cover in its deployed position, even under extreme wind loads and road vibration.